Diazotype reproduction material



United States Patent Ofiice 3,3215 l Patented May 23, 1&6?

3,321,310 DIAZOTY PE REPRODUCTION MATERIAL Charles J. Fox, Charlotte. N.C., assignor to Hercuies incorporated, a corporation of Delaware No Drawing. Filed Jan. 7, 1964, Ser. No. 336,109

4 Claims. (Cl. 96-75) This invention relates to diazotype reproduction material and more particularly to a coating composition for the base of said material which may be applied prior to or simultaneously with the application of a conventional sensitizing composition containing a light-sensitive diazo compound.

Several types of diazotype reproduction material comprising a light-sensitive layer containing a light-sensitive diazo compound on paper or cloth base are known. One such type commonly referred to as one-component diazotype material comprises a light-sensitive layer containing a light-sensitive diazo compound on a base. After exposure of the paper to ultraviolet light under a positive the image is developed by coupling the unexposed diazo compound with an azo coupling component present in the developing solution.

Another type of such material commonly referred to as two-component comprises a light-sensitive layer containing both a light-sensitive diazo compound and a coupling agent therefor which are stabilized against premature coupling on a base. In the latter type, development is carried out by treating the material under proper conditions, e.g., by exposure to alkaline conditions.

The foregoing diazotype materials are objectionable sincethey result in prints having relatively poor dye line density, color non-uniformity of half-tone regions, and bleeding of dyed regions into non-dyed regions.

In an attempt to improve such diazotype materials, several coating compositions have been proposed. Aqueous dispersions of colloidal and non-colloidal silica have been proposed as coating compositions. However, their use either prior to or simultaneously with the application of the sensitizing composition is not without undesirable effects. Colloidal silica is deleterious to print uniformity when used on base material having a White background. Non-colloidal silica will usually settle out and tends to rub off when the print surface contacts other material. Improved results relative to the use of silica have been obtained by using ungelatinized granular rice starch as a coating composition for diazotype reproduction material as is disclosed in US. Patent No. 2,780,547. A serious drawback to extensive use of rice starch in diazotype reproduction material has been the relatively high cost of the rice starch.

It has also been proposed (Canadian Patent No. 637,- 448) that other types of starch, for example, corn, wheat, tapioca, potato and the like, he used in place of rice starch in diazotype reproduction material coating compositions, provided that either colloidal or non-colloidal silica is incorporated with the starch granules and binder. In addition, the starch granules are preferably reduced in particle size before use. The term granule is used herein to mean a unit of starch in its naturally occurring state.

It is an object of this invention to provide improved coating compositions for diazotype reproduction material. Another object is to provide such a coating composition which will result in prints having greater color uniformity of half-tone regions, increased dye line density and less bleeding of dyed regions into non-dyed regions.

The above and other objects of providing improved diazotype reproduction material are accomplished by applying to the base of such material an aqueous dispersion of ungelatinized Wheat starch having a granule size of 2- microns to coat said base with said wheat starch and also applying to said base a sensitizing solution containing a light-sensitive diazo compound covering said wheat starch. The sensitizing solution containing the light-sensitive diazotype compound may be incorporated into the wheat starch dispersion and both applied to the base simultaneously or, if preferred, the wheat starch coating may be applied to the base prior to application of the sensitizing solution.

Surprisingly, we have found that coating the base of diazotype reproduction material with ungelatinized wheat starch having a granule size of 2-10 microns applied as a dispersion in an aqueous medium, said what starch coating being covered with a sensitizing solution containing a light-sensitive diazo compound, results in prints having greater color uniformity of half-tone regions, increased dye line density and less bleeding of dyed regions into non-dyed regions than was heretofore possible using prior art techniques. It is Well known that naturally occurring wheat starch granules are either large or small with vfew granules of intermediate size. The larger granules are within the range of 20-35 microns. The smaller granules are within the range of 2-10 microns. All known applications of wheat starch use wheat starch granules of the larger size range. The large size granules are obtained by physical separation of the smaller granules from naturally occurring wheat starch granules. It is the separated material (2-10 microns), which is normally discarded, that is applicable to this invention. Of course, it is to be understood that the physical separation of the larger granules from naturally occurring wheat starch granules is not always percent effective and that, therefore, the smaller granule range may contain a very small number of granules from the larger size range as well as a very small number of granules from the intermediate size range.

As uscd herein the size limitation of wheat starch granules (2-10 microns) means wheat starch granules of the smaller size range (2-10 microns) which may have a very small number of granules from both the larger size range and the intermediate size range admixed therewith.

Those skilled in the art know that the amount of starch applied as coating is not critical and may be varied widely. Good results have been obtained in accordance with this invention by applying the aqueous dispersion of ungelatinized wheat starch having a granule size of 2-10 microns in an amount suflicient to coat the base with 0.5- 5 grams wheat starch per square meter of surface.

The aqueous dispersion of the ungelatinized wheat starch granules may be applied to the base over a wide range of temperature. The critical aspect is not the temperature of application, but the fact that the wheat starch granules must be substantially ungelatinized, i.e. noncooked and substantially non-swollen. Of course, one would operate below the gelatinization temperature of the wheat starch to insure the use of non-cooked and substantially non-swollen wheat starch granules; but this temperature, normally F., may vary when the dispersion is alkaline or if gelatinization inhibitors are used. G'enerally, the application of theaqueous dispersion of ungelatinized wheat starch having a granule size of 2-10 microns is preferably carried out at room temperature, i.e. 66 F.-76 F.

The base material for the diazotype reproduction material may be paper commonly known as direct process paper or filled or sized cloth such as blueprint cloth. The

papers are normally surface-sized papers sized with starch or glue as is well known in the paper making art.

While the 2-10 microns granule size ungelatinized wheat starch of this invention may be applied alone to the base, it is preferred to use a binder along with the wheat starch that will bond the wheat starch granules to 3 each other and to the base. Any binder which will bond the wheat granules to each other and to the base may be used provided it is compatible with the sensitizing solution and does not adversely affect coupling or interfere with print smoothness and dye line density. The preferred binders for diazotype reproduction material are polyvinyl acetate emulsions. Other binders which may be used are methyl cellulose, carboxymethylcellulose, polyvinyl a1- cohols, polyvinyl pyrrolidone, gum arabic, gum tragecanth, alginates, acrylic emulsions, gelatin glues, caseinates, water-soluble styrene polymers, cooked starches and starch derivatives such as hydroxypropyl starch, hydroxyethyl starch, carboxymethyl starch and carboxymethyl hydroxypropyl starch.

The amount of binder used is not critical and will depend in part upon the particular binder selected. Generally about /225 parts of ungelatinized wheat starch of 2-10 microns granule size may be used per part of binder. Likewise, the amount of ungelatinized wheat starch of 2-10 microns granule size contained in the aqueous dispersion is not critical and may be varied to suit specific operating methods and conditions. Generally the aqueous dispersion should contain about 1% to 30% by weight of the ungelatinized wheat starch of 2-10 microns granule size.

Any of the known compounds employed in the production of diazotype reproduction materials may be used as the light-sensitive diazo compound. Examples of such compounds are diazonium compounds obtained by diazotization of the following amines:

3-chloro-4-diethylamino-aniline 2-amino-5-dimethylamino-benzoic acid p-amino-diphenylamine N-fi-hydroxyethyl-N-methyl-p-phenylenediamine N-fl-hydroxyethyl-N-ethyl-p-phenylenediamine Nbenzyl-N-ethyl-p-phenylenediamine N,N-di- B-hydroxyethyl -p-phenylenediamine p-phenylenediamine p-ethylamino-m-toluidine p-dimethylamino-o-toluidine p-diethylamino-o-phenetidine p- N-ethyl-N-/8-hydroxyethylamino -o-toluidine p-diethylamino-aniline p-dimethylamino-aniline 4-benzoylamino-2,5-diethyoxyaniline p-di-B-hydroxyethylamino-o-chloroaniline p-ethylamino-aniline 2,5 -diethoxy-4- 4-ethoxyphenylamino -aniline Diazonium compounds and combinations thereof obtained from the above amines, in the form of their stable diazonium sulfates, or borofiuorides, or in the form of the soluble salts of the diazonium chloride with zinc chloride, cadmium chloride or stannic chloride.

Coupling components suitable for use in the sensitizing compositions or in the diazotype light-sensitive layer may be any of the following:

1-( sulfophenyl) -3-methyl-pyrazolone-5 p-sulfo-acetoacetamide 1,8-dihydroxynaphthalene-3,6-disulfonic acid 2,3-dihydroxy naphthalene 2,3-dihydroxy naphthalene-6-sulfonic acid ,B-hydroxyethylamide of 2-hydroxy-3-naphthoic acid fi-naphthol resorcinol-S- sulfonic acid phloroglucinol carboxylic acid 2,4,4-trihydroxy-biphenyl-2-sulfonic acid 2-naphthol-3,6-disulfonic acid resorcinol phloroglucinol 2,2',4,4'-tetrahydroxy-biphenyl The foregoing coupling components can be employed alone or in combinations of two or more to obtain the desired image coloration.

Aqueous dispersions of the following four starches were prepared.

(1) Ungelatinized wheat starch having a granule size of 2-10 microns.

(2) Ungelatinized rice starch.

(3) Ungelatinized wheat starch having a granule size greater than 10 microns.

(4) The ungelatinized wheat starch of (3) above the granules of which were mechanically reduced to 2-10 microns (ball mill and water sedimentation).

Aqueous dispersions of starches 1, 2 and 3 above were prepared by the formula shown below:

Grams Starch 5O Polyvinyl acetate emulsion (55% solids) 25 Water The aqueous dispersion of starch Number 4 above was prepared by the following formula:

Grams Starch paste (21.5% solids) 11.5 Polyvinyl acetate emulsion (55% solids) 5.6 Water 67 Starch dispersions 1, 2, 3 and 4 above were then applied to separate sheets of starch sized direct process paper by a coating roll so that uniform distribution of the starch was obtained. Each specific starch dispersion was applied to three sheets in amounts within the range of 1-3 grams of wheat starch per square meter of surface. The coatings were then dried and sensitized with the following solution:

1% alum 2% thiourea 2% ammonium oxalate 0.1% saponin 2.5% p-diazo-N,N-diethylaniline, zinc chloride salt the rest being water.

After drying the papers, prints were made in a contact printer containing five l5-watt, 360 BL Westinghouse ultraviolet tubes. A inch thick glass plate, 3 inches from the surface of the light, served as the support for the negative and diazo paper. The image transparency contained a bulls eye pattern consisting of regions of fine lines and half-tone dots of varying sizes. Exposure times of 5, 8 and 20 minutes were used. Exposure time is not critical. Other times could be used as is well known in the art, depending on exposure conditions.

The prints thus made were developed with an alkalinetype developer containing:

' Percent Borax 4.4 Sodium carbonate 2.2 Thiourea 1.8 Resorcinol 0.7 Phloroglucinol 0.7 Mannitol 2.6 Sodium isopropyl naphthalene sulfonate 0.2

The rest being water.

The developed prints thus prepared were mounted on a board and compared against each other at the various irradiation times using visual examination of the black images on white paper. The coated papers were compared with each other and with a control sample of uncoated paper in regard to dye line density, color uniformity of half-tone regions, and bleeding of dyed regions into nondyed regions.

The results of the visual examination at the various irradiation times were averaged and are given in Table 1. The lowest number indicates the superior rating. In cases where no major diiIerences were obvious, samples were ranked equivalent.

The same procedure was followed as in Example 1 except that the starch coating compositions and the respective sensitizing solutions were incorporated and applied simultaneously to the diazotype reproduction base papers.

Substantially the same improvement (see Table 1 hereinbefore) for wheat starch having a granule size of 2-10 microns is obtained when the starches are used as carrier for the sensitizing solution containing the lightsensitive diazo compound.

From the foregoing, it is apparent that ungelatinized wheat starch having a granule size of 2-10 microns applied as an aqueous dispersion to diazotype reproduction base material either prior to or simultaneously with the application of a sensitizing solution in accordance with this invention results in prints having substantially improved images when compared to prints made using prior art techniques. As compared to prints made from paper coated with wheat starch having a granule size greater than microns and wheat starch of reduced particle size, this invention quite unexpectedly results in prints having improved color uniformity of half-tone regions and far superior dye-line density. When compared to prints made from paper coated with the more expensive rice starch, the use of this invention results in prints having increased dye-line density. Thus, this invention provides the art with an economical wheat starch coating composition for diazotype reproduction material which is superior to rice starch and which does not require particle size reduction of the wheat starch and the use of additives.

As many apparent and widely different embodiments of this invention may be made without departing from the spirit and scope thereof, it is to be understood that We do not limit ourselves to the specific embodiment thereof except as defined in the appended claims.

What I claim and desire to protect by Letters Patent is:

1. Diazotype reproduction material comprising a base sheet coated with (1) ungelatinized Wheat starch having a granule size of at least 2 but not greater than 10 microns and 2) a sensitizing composition containing a light-sensitive diazo compound.

2. Diazotype reproduction material comprising a base sheet coated with (1) ungelatinized wheat starch having a granule size of at least 2 but not greater than 10 microns and (2) a mixture comprising a sensitizing composition containing a light-sensitive diazo compound and a coupling agent for said light-sensitive diazo compound.

3. Diazotype reproduction material comprising a base sheet coated with (1) a mixture of a binder and ungelatinized wheat starch having a granule size of at least 2 but not greater than 10 microns and (2) a sensitizing composition containing a light-sensitive diazo compound.

4. Diazotype reproduction material comprising a base sheet coated with (1) a mixture of a binder and ungelatinized wheat starch having a granule size of at least 2 but not greater than 10 microns and (2) a mixture comprising a sensitizing composition containing a light-sensitive diazo compound and a coupling agent for said light sensitive diazo compound.

References Cited by the Examiner UNITED STATES PATENTS 2,662,013 12/1953 Sulich et al. 96--75 2,709,655 5/1955 Frederick 9675 2,780,547 2/1957 Ferzola et al 9675 3,155,511 11/1964 Jahoda et al 9675 3,159,487 12/1964 Kreiger et al. 9691 FOREIGN PATENTS 637,448 2/1962 Canada. 841,131 7/1960 Great Britain.

NORMAN G. TORCHIN, Primary Examiner.

ALEXANDER D. RICCI, Examiner.

C. L. BOWERS, Assistant Examiner.

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3,321,310 May 23, 1967 I Charles J. Fox

It is hereby certified that error appears in the above numbered patent requiring correction and that the said Letters Patent should read as corrected below.

Column 2, line 12, for "what" read wheat column 3, line 53, for "soluble" read double Signed and sealed this 26th day of December 1967.

(SEAL) Attest:

EDWARD J. BRENNER Edward M. Fletcher, Jr.

Attesting Officer Commissioner of Patents 

1. DIZAOTYPE PRODUCTION MATERIAL COMPRISING A BASE SHEET COATED WITH (1) UNGELANTINIZED WHEAT STARCH HAVING A GRANULE SIZE OF AT LEAST 2 BUT NOT GREATER THAN 10 MICRONS AND (2) A SENSITIZING COMPOSITION CONTAINING A LIGHT-SENSITIVE DIAZO COMPOUND. 